ABSTRACT The goal of Project 2: ?Neisserial outer membrane vesicle vaccines? within the Gonorrhea Vaccine Cooperative Research Center (GV CRC) is to develop candidate Neisseria gonorrhoeae (Ng) and Neisseria meningitidis (Nm) OMV vaccines that protect against gonorrhea. The premise of this application is that an effective gonorrhea vaccine can be developed using neisserial OMVs containing defined surface exposed, protective antigens. This premise is supported by exciting new epidemiological evidence that serogroup B Nm OMVs can reduce the risk of gonorrhea and preliminary data from our laboratories that show two different Nm OMV-based vaccines accelerate clearance of Ng from experimentally infected mice. The Specific Aims of the application are to: 1) Further develop a novel Nm OMV vaccine that demonstrates in vivo efficacy against Ng, 2) Develop Ng OMV vaccines with increased expression of promising vaccine targets, and 3) Develop next-generation Ng and, or Nm OMV vaccines consisting of OMVs combined with nanodisc-displayed protein vaccines or Ng epitope-targeted virus-like-particle vaccines being developed by other GV CRC investigators. OMVs will undergo standardized quality control for structural integrity and composition and a rigorous pre-clinical assessment using state-of-the art assays for measuring host immune responses and in vivo efficacy in mouse models of Ng lower and upper reproductive tract (LRT, URT) infection. The most promising vaccines, defined by the capacity to induce systemic and mucosal humoral and cellular immune responses and protect against murine genital tract infection, will be selected for advancement to further pre-clinical testing and clinical trials. We will also test the effect of licensed adjuvants on alleviating Ng- induced immunosuppression of Ng OMV vaccine efficacy and utilize the database of immune responses and in vivo protection data obtained from all candidate vaccines to define mechanisms of vaccine-induced immunity.